The present invention relates to a process for producing an optically active hemiester.
An optically active hemiester, for example, an imidazolidin 2-one hemiester derivative has been known as an intermediate for synthesizing d-biotin (vitamin H) and the like. There have been known a process for producing hemiester intermediate derivatives by ring-opening reactions of a cyclic acid anhydride using a complex of alkaloids and dialkylzinc as described in Bull. Chem. Soc. Jpn, 1993, 66, 2128, and a process of using an optically active diisopropoxytitanium TADDOLate as described in J. Org. Chem, 1998, 63, 1190.
According to the present invention, an optically active hemiester with good optical activity can be industrially advantageously obtained.
The first aspect of the present invention relates to a process for producing an optically active hemiester of formula (1): 
wherein R1, R2 and R3 represent the same meanings as described below, which comprises reacting a cyclic acid anhydride of formula (2); 
with a hydroxy compound of formula (3):
R3OH xe2x80x83xe2x80x83(3) 
in the presence of an asymmetric catalyst comprising
a Lewis acid compound selected from a halide, alkoxide or trifluoromethanesulfonate of an element of Group 3, 4, 13 or 14 of Periodic Table of the Elements, and
an optically active ligand selected from a diol, aminoalcohol or bisoxazoline compound, wherein in formulae (1), (2) and (3) R1 and R2 are different and independently represent
a hydrogen atom, a halogen atom,
an alkyl group optionally substituted with an alkoxy group or a halogen atom,
an alkenyl group optionally substituted with an alkoxy group or a halogen atom,
an aralkyl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom,
an aryl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom, or
a group of formula(10): RaOxe2x80x94, RbNH, or RaRbN, wherein
Ra represents
an alkyl group, an aralkyl group, a silyl group, or an acyl group, and
Rb represents
an acyl group, an alkoxycarbonyl group, an aralkyloxycarbonyl group, an alkylsulfonyl group, a haloalkylsulfonyl group or an arylsulfonyl group, or
either R1 groups or R2 groups may be bonded at their terminals to form a ring; and
R3 represents
an alkyl group optionally substituted with an alkoxy group, a phenoxy group, a dialkylamino group or a halogen atom,
an aralkyl group optionally substituted with an alkyl group, an alkoxy group, a phenoxy group, a nitro group or a halogen atom,
an aryl group optionally substituted with an alkyl group, an alkoxy group, a nitro group or a halogen atom.
The second aspect of the present invention relates to
a process for producing an optically active imidazolidin-2-one of formula (4): 
wherein R21 represents the same as defined below and R3 represent the same as defined above,
which comprises reacting a cyclic acid anhydride of formula (5): 
wherein R21 represents
an alkyl group optionally substituted with an alkoxy group or a halogen atom,
an aralkyl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom,
an aryl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom, with a hydroxy compound of formula (3):
R3OH xe2x80x83xe2x80x83(3) 
wherein R3 is the same as defined above, in the presence of an optically active alkaloid selected from quinine, epiqunine, cinconine and cinconidine.
The first aspect of the present invention will be explained first. In the cyclic acid anhydride of formula (2), examples of the halogen atom represented by R1 or R2 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom,
Examples of the alkyl group optionally substituted with an alkoxy group or a halogen atom represented by R1 or R2 include
a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, which alkyl group may be optionally substituted with a halogen atom, an alkoxy group (e.g., a (C1-C5)alkoxy group such as methoxy, ethoxy, n-propoxy, or i-propoxy group, i-butoxy group, s-butoxy group, t-butoxy group, n-pentyloxy group, i-pentyloxy group, or neo-pentyloxy group) and the like.
Specific examples of the optionally substituted alkyl group include
a methyl group, an ethyl group, a n-propyl group, a i-propyl group, a n-butyl group, a i-butyl group, a s-butyl group, a t-butyl group, a n-pentyl group, isoamyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a chloromethyl group, a dichloromethyl group, a trichloromethyl group, a bromomethyl group, a 1-chloroethyl group, a 2-chloroethyl group, a 1,2-dichloroethyl group, a 2,2,2-tricliloroethyl group, a methoxymethyl group, a 2-metoxyethyl group and the like.
Examples of the alkenyl group optionally substituted with an alkoxy group or a halogen atom include a (C2-C3)alkenyl group optionally substituted with an (C1-C5)alkoxy group or a halogen atom, Specific examples thereof include a vinyl group, a propen-1-yl group, a propen-2-yl group, a 2-methylpropen-1-yl group, a 2,2-dichlorovinyl group, a 2,2-dibromovinyl gorup, a 2-methoxyvinyl group and the like.
Examples of the aralkyl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom include a (C7-C11)aralkyl group optionally substituted with a (C1-C5)alkyl group (e.g., a methyl group, an ethyl group, n-propyl group, i-propyl group or n-butyl group, s-butyl group, t-butyl group, n-pentyl group, i-pentyl group, or neo-pentyl group), a (C1-C5)alkoxy group, or a halogen atom.
Specific examples thereof include a benzyl group, a 1-phenethyl group, a 2-phenethyl group, an xcex1-naphthylmethyl group, a xcex2-naphthylmethyl group and the like, of which aromatic rings may be optionally substituted with at least one group selected from the halogen atom, the alkoxy group or the alkyl group as described above.
Examples of the aryl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom include a (C6-C18)aryl (e.g.,a phenyl, naphthyl, anthranyl or phenanthryl) group which may be optionally substituted with the halogen atom, the (C1-C5)alkyl or (C1-C5)alkoxy group as described above and the like.
Examples of the alkyl group, aralkyl group, silyl group, or acyl group represented by Ra respectively include
a (C1-C5)alkyl group such as a methyl group, an ethyl group, a propyl group, a n-butyl group, t-butyl group, a pentyl group or the like
a (C7-C8)aralkyl group such as a benzyl group or a phenethyl group,
a silyl group having three (C1-C4)alkyl groups such as a trimethylsilyl group, a t-butyldimethylsilyl group or the like,
a (C2-C6)acyl group such as an acetyl group, a benzoyl group or the like.
Examples of the acyl group represented by Rb include the same acyl groups as described above. Examples of the alkyl group in the alkoxycarbonyl group or alkylsulfonyl group, and examples of the aralkyl group in the aralkyloxycarbonyl group respectively include the same groups as defined above for Ra.
Specific examples of the aryl sulfonyl group include a p-toluenesulfonyl group, or the like. Specific examples of the alkylsulfonyl group include a methylsulfonyl group. Specific examples of the haloalkylsulfonyl group include a trifluoromethanesulfonyl group and the like.
Examples of the group formed by either R1 groups or R2 groups include a group of following formula (9):
xe2x80x94(CH2)nxe2x80x94, xe2x80x83xe2x80x83(9a) 
wherein n is an integer of 2 to 4,
xe2x95x90C(CH3)2, xe2x80x83xe2x80x83(9b) 
xe2x80x94NR21CON(R21)xe2x80x94xe2x80x83xe2x80x83(9c) 
wherein R21 represents the same as defined above in connection with formula (5), or 
wherein X represents
xe2x80x94Oxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94CH2xe2x80x94, or xe2x80x94(CH2)2xe2x80x94, and
Y represents xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94(CH2)2xe2x80x94.
Substituents represented by R21 are explained below.
The alkyl group optionally substituted with an alkoxy group or a halogen atom include a linear, branched or cyclic (C1-C10)alkyl group optionally substituted with a halogen atom or a (C1-C6)alkoxy group.
The aralkyl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom include a (C7-C11)aralkyl group optionally substituted with a halogen atom, a (C1-C5)alkoxy group or a (C1-C5)alkyl group (e.g, a benzyl group or the like).
The aryl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom include a (C6-C18)aryl group optionally substituted with a halogen atom, a (C1-C5)alkyl group or a (C1-C5)alkoxyl group.
Preferred are the aralkyl group described above. Particularly preferred is a benzyl group.
In R1 and R2 groups, either R1 or R2 groups are preferably hydrogen atoms. The group formed by R1 or R2 groups of formula (9c) above is preferred.
Specific examples of the cyclic acid anhydride of formula (2) include
(3R, 4S)-dimethyl-3,4-dihydrofuran-2,5-dione,
3-oxabicyclo[3.2.0]heptan-2,4-dione,
2,4,5,6,3a,6a-hexahydro-2-oxapentalen-1,3-dione,
4,5,6,7,3a,7a-hexahydroisobenzofuran-1,3-dione,
6,6-dimethyl- -oxabicyclo[3.1.0]hexan-2,4-dione,
4,10-dioxatricyclo[5.2.1.0 less than 2,6 greater than ]decan-3,5-dione,
4,10-dioxatricyclo[5.2.1.0 less than 2,6 greater than ]dec-8-ene-3,5-dione,
4-oxatricyclo[5,2,1,0 less than 2,6 greater than ]decan-3,5-dione,
4-oxatricyclo[5.2.1.0 less than 2,6 greater than ]dec-8-ene-3,5-dione,
4-oxacyclo[5.2.2.0 less than 2,6 greater than ]undecan-3,5-dione,
4-oxatricyclo[5.2.2.0 less than 2,6 greater than ]undec-8-ene-3,5-dione,
4,6-bisbenzyl-2,4-6-3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione
4,6-dimethyl-2,4,6,3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione,
4,6-bisbenzyl-2,4,6,3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione,
4,6- diphenyl-2,4,6,3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione
and the like. Anhydrides as described above are commercially available.
The R3 group of the hydroxy compound of formula (3) will be explained below.
Examples of the alkyl group optionally substituted with an alkoxy group, a phenoxy group, a dialkylamino group or a halogen atom include a (C1-C8)alkyl group optionally substituted with a (C1-C5)alkoxy group, a phenoxy group, a di(C1-C3)alkylamino group, or a halogen atom.
Examples of the aralkyl group optionally substituted with an alkyl group, an alkoxy group, a phenoxy group, a nitro group or a halogen atom include a (C7-C8)aralkyl group (e.g, a benzyl group or a 1-, or 2-phenethyl group) optionally substituted with a (C1-C5)alkyl group, a (C1-C5)alkoxy group, a phenoxy group, a nitro group or a halogen atom.
Examples of the aryl group optionally substituted with an alkyl group, an alkoxy group, a nitro group or a halogen atom include a phenyl group optionally substituted with a (C1-C5)alkyl group, a (C1-C5)alkoxy group, a nitro group, or a halogen atom.
In the examples above, the (C1-C5)alkyl group or the (C1-C5)alkoxy group are the same as defined above for the substituent groups in R1 and R2.
Examples of the hydroxy compound of the formula (3) include an alkyl alcohol having said alkyl group as defined above, an aralkyl alcohol having said aralkyl group as defined above, an aryl alcohol having said aryl group as defined above and the like.
Specific examples thereof include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, s-butyl alcohol, t-butyl alcohol, n-pentyl alcohol, neopentyl alcohol, amyl alcohol, hexyl alcohol, octyl alcohol, 2-methoxyethanol, 2-phenoxyethanol, 2- (dimethylamino)ethanol, 2-chloroethanol, benzyl alcohol, 2-methylbenzyl alcohol, 4-methylbenzyl alcohol, 2-methoxybenzyl alcohol, 4-methoxybenzyl alcohol, 2-phenoxybenzyl alcohol, 4-phenoxybenzyl alcohol, 4-nitrobenzyl alcohol, 4-cholorobenzyl alcohol, phenol, 2-methylphenol, 4-methylphenol, 2-methoxyphenol, 4-methoxyphenol, 4-nitrophenol, 4-chlorophenol and the like.
Among the R3 of the hydroxy compound of formula (3), preferred are the alkyl group optionally substituted with an alkoxy group, a phenoxy group, a dialkylamino group or a halogen atom, and
the aralkyl group optionally substituted with an alkyl group, an alkoxy group, a phenoxy group, a nitro group or a halogen atom.
More preferred are primary alcohols of formula R33CH2OH, wherein R33 represents
a (C1-C7)alkyl group optionally substituted with a (C1-C5)alkoxy group, a phenoxy group, a di(C1-C3)alkylamino group, or a halogen atom, or
a phenyl group optionally substituted with a (C1-C5)alkyl group, a (C1-C5)alkoxy group, a phenoxy group, a nitro group, or a halogen atom.
An amount of the hydroxy compoud (3) is not particularly limited, and the compound may be used, as a solvent, in excess to the cyclic acid anhydride (2), and may be recovered after completion of the reaction, for example, by distillation or the like. An amount of the hydroxy compoud (3) is typically 1 mole or more per mol of the cyclic acid anhydride (2).
The asymmetric catalyst to be used in the present process can be prepared by contacting a Lewis acid compound selected from a halide, alkoxide or trifluoromethanesulfonate of an element of Group 3, 4, 13 or 14 of Periodic Table of the Elements with an optically active ligand selected from a diol, aminoalcohol and bisoxazolidine compound.
Examples of the Lewis acid compound selected from a halide, alkoxide or trifluoromethanesulfonate of an element of Group 3, 4, 13 or 14 of Periodic Table of the Elements include
a boron halide such as boron trifluoride, boron trichloride,
an aluminium halide or alkoxide such as aluminium trichloride, aluminium triisopropoxide or the like,
a tatinium halide or alkoxide such as titanium tetrachloride, titanium tetraisopropoxide or the like,
a tin halide such as tin tetrachloride, tin dichloride or the like,
a lanthanum alkoxide such as lanthanum triisopropoxide or the like, and scandium triflate (trifluoromethanesulfonate) or the like. In particular, tin dichloride and titanium tetraisopropoxide are preferred.
Examples of the optically active ligand include
an optically active amino alcohol of formula (7): 
wherein R8 and R9 are different and R6, R7, R8, R9, R10 and R11 independently represent
a hydrogen atom,
an optionally substituted alkyl group,
an optionally substituted alkenyl group,
an optionally substituted aryl group, or R9 and R10 may be bonded to form an optionally substituted alkylene, and
an optically active bisoxazolidine of formula (8): 
wherein R12 represents
a hydrogen atom,
an optionally substituted alkyl group, or
an optionally substituted aryl group, wherein two geminal alkyl groups may be bonded at their terminals to form a ring(e.g., an alkylene group),
R13 represents
an optionally substituted alkyl group,
an optionally substituted aryl group, and
R14 represents
a hydrogen atom,
an optionally substituted alkyl group,
an optionally substituted aryl group, and
the carbon atoms denoted by xe2x80x9c*xe2x80x9d represent asymmetric carbon atoms having an S or R configuration.
Examples of the optically active diol compound include optically active 1,1-binaphthol, 1,2-diphenylethan 1,2-diol and the like.
In R6-R11 of the optically active aminoalcohol of formula (7) will be explained below.
The optionally substituted alkyl group includes
an alkyl group optionally substituted with an alkoxy group or a halogen atom (e.g., a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms optionally substituted with a halogen atom, or a(C1-C5)alkoxy group), and
an aralkyl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom (e.g., a (C7-C11)aralkyl group optionally substituted with a (C1-C5)alkyl group, a (C1-C5)alkoxy group, or a halogen atom).
The optionally substituted alkenyl group includes
an alkenyl group optionally substituted with an alkoxy group or a halogen atom(e.g., a (C2-C3)alkenyl group optionally substituted with an (C1-C5)alkoxy group or a halogen atom).
The optionally substituted aryl group includes
an aryl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom (a (C6-C18)aryl (e.g.,a phenyl, naphthyl, anthranyl or phenanthryl) group which may be optionally substituted with a halogen atom, a (C1-C5)alkyl or (C1-C5)alkoxy group).
Examples of the optionally substituted alkylene group include an ethylene or trimethylene group, which may be fused with a benzene ring (e.g., an indanyl group or the like).
With respect to the specific examples of these groups, those described above for R1 and R2 can be referred to.
In the optically active bisoxazoline of formula (8), the optionally substituted alkyl group, and the optionally substituted aryl group respectively have the same meaning as defined above in connection with formula (7).
Specific examples of the optically active ligand include optically active
1,1-binaphthol, 1,2-diphenylethan-1,2-diol,
2-amino-1,1-diphenyl-3-phenylpropan-1-ol, 1-amino-2-indanol,
2-amino-1-indanol, 2-amino 1,1-diphenyl-2-phenylethan-1-ol,
2-amino-1-diphenyl-3-methylbutan-1-ol,
2-amino-1,1-bis[2-butoxy-4-(2-methylpropan-2-yl)phenyl]-3-phenylpropan-1-ol,
2-amino-1,1-bis[2-butoxy-4-(2-methylpropan-2-yl)phenyl]-2-phenylethan-1-ol,
2-amino-1,1-bis[2-butoxy-4-(2-methylpropan-2-yl)phenyl]-3-methylbutan-1-ol,
2-aminocyclopentanol, 2-aminocyclohexanol,
2,2xe2x80x2-isopropylidenebis(4-t-butyl-2-oxazoline),
2,2xe2x80x2-isopropylidenebis(4-phenyl-2-oxazoline),
2,2xe2x80x2-methylenebis(4-pheuyl-2-oxazoline) and the like.
Preferred are optically active aminoalcohol and bisoxazoline, more preferred are 2-amino-1,1-bis[2-butoxy-4-(2-methylpropan-2-yl)-phenyl]-3-phenylpropan-1-ol and 2,2xe2x80x2-isopropylidenebis(4-t-butyl-2-oxazoline).
The optically active ligands are commercially available or the optically active oxazoline can be produced according to a reference such as EP895992A or the like.
An amount of the Lewis acid compound to be used is not particularly limited but it is usually catalytic amount, for example, around 0.00001 to less than 1 mole, preferably around 0.0001 to 0.5 mole per mol of the cyclic acid anhydride (2).
An amount of the optically active ligand is not particularly limited but it is usually around 1 to 10 moles, preferably around 1 to 2 moles per mol of the Lewis acid compound. Said asymmetric catalyst can be produced by a process comprising contacting said Lewis acid compound with said optically active ligand, and thus formed catalyst may be isolated prior to use, alternatively, said catalyst may be prepared in situ. For example, said process of contacting said Lewis acid compound with said optically active ligand may be conducted simultaneously in a reaction system of reacting the cyclic acid anhydride (2) with the alcohol compound (3).
The reacting of the cyclic acid anhydride (2) with an alcohol compound (3) may be carried out in the co-presence a base selected from an inorganic base or an aromatic tertiary amine compound.
Examples of the inorganic base include
a carbonate or bicarbonate of an alkali metal and a carbonate of alkaline earth metal (e.g., lithium carbonate, potassium carbonate, sodium carbonate, lithium hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, magnesium carbonate), and ammonium carbonate, and
Examples of the aromatic tertiary amine compound include N-methylimidazole, a pyridine compound (e.g, a pyridine compound optionally substituted with an alkyl or a halogen atom such as pyridine, 2-methyl-5-ethylpyridine, 2,6-dichloropyridine, picoline or the like) and the like.
Preferred are a carbonate or bicarbonate of an alkali metal or a carbonate of alkaline earth metal such as sodium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, or magnesium carbonate, and a pyridine compound such as 2,6-dichloropyridine.
An amount of the base to be used is not particularly limited but it is usually around 10 moles or less, preferably around 2 moles or less per mol of the cyclic acid anhydride (2).
The reaction of the cyclic acid anhydride (1) with the hydroxy compound (3) is usually conducted in an inert gas atmosphere such as argon, nitrogen and the like. The reaction may be performed under a normal, pressurized or reduced pressure.
The reaction may be performed without a solvent or in a solvent. Examples of the solvent to be used include
a halogenated aliphatic hydrocarbon such as dichloromethane, chloroform, 1,2-dichloromethane and the like,
an aliphatic hydrocarbon such as hexane, heptane, octane, nonane, or the like,
an aromatic hydrocarbon such as benzene, toluene, xylene,
a halogenated aromatic hydrocarbon such as chlorobenzene or the like,
an ether solvent such as diethyl ether or tetrahydrofuran, and
a mixed solvent thereof.
A reaction temperature is not particularly limited but it is usually in a range of xe2x88x9280 to 100xc2x0 C., preferably xe2x88x9250 to 50xc2x0 C.
After completion of the reaction, the catalyst can be removed from optically active hemiesters (3) by washing with water or acidic water and the product can be readily separated from the reaction mixture by usual post treatment such as extraction, phase separation, distillation or the like, and it may be further purified by column chromatography or the like, if necessary. The organic base may be recovered, for example, by adding a strong base to the separated aqueous phase.
Next, a description will be made to the second aspect of the present invention, which relates to a process for producing an optically active imidazolidin-2-one of formula (4), which comprises reacting a cyclic acid anhydride of formula (5) with a hydroxy compound of formula (3) in the presence of an optically active alkaloid selected from quinine, epiquinine, cinchonine and cinchonidine.
In formula (4) and (5), R21 is the same as defined above in connection with formula (9c). R21 is preferably the aralkyl group optionally substituted with an alkyl group, an alkoxy group or a halogen atom, and more preferably a benzyl group.
Examples of the cyclic acid anhydride of formula (5) include 4,6-dimethyl-2,4,6,3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione, 4,6-bisbenzyl-2,4,6,3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione, 4,6-diphenyl-2,4,6,3a,6a-pentahydro-4,6-diaza-2-oxapentalen-1,3,5-trione and the like.
Among the optically active alkaloid, quinine is preferred.
An amount of the optically active alkaloid to be used is not particularly limited and is usually around 0.00001 to 1 mole or may be catalytic amount, for example, less than 1 mol per mol of the cyclic acid anhydride (2).
The reaction is preferably carried out in the co-presence of a base, Examples of the base include an inorganic base (e.g., a carbonate or bicarbonate of an alkali metal or a carbonate of alkaline earth metal such as lithium carbonate, potassium carbonate, sodium carbonate, lithium hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, magnesium carbonate or the like), and ammonium carbonate, and
an aliphatic or aromatic tertiary amine compound such as trimethylamine, ethyldiisopropylamine, pyridine, 1,2,2,6,6-pentamethyl piperidine, 2-methyl-5-ethylpyridine, 2,6-dichloropyridine, picoline, N-methylimidazole and the like. In particular, 1,2,2,6,6-pentamethyl piperidine is preferred.
An amount of the base to be used is not particularly limited but is usually around 0.1 to 10 moles, preferably around 0.1 to 2 moles per mol of the cyclic acid anhydride (5).
The reaction of the cyclic acid anhydride (5) with the hydroxy compound (3) is conducted in the presence of the optically active alkaloid, and usually in an inert gas atmosphere such as argon, nitrogen and the like. The reaction may be performed either under a normal, pressurized or reduced pressure.
The reaction can be performed without a solvent or in a solvent. Examples of the solvent to be used include a halogenated hydrocarbon such as dichloromethane, chloroform, 1,2-dichloroethane, carbon tetrachloride and the like, an aliphatic hydrocarbon such as hexane, heptane, octane and nonane, an aromatic hydrocarbon such as benzene, toluene, xylene, or the like, a halogenated aromatic hydrocarbon such as chlorobenzene and the like, an ether solvent such as diethyl ether and tetrahydrofuran, and a mixed solvent thereof.
A reaction temperature is not particularly limited and is usually in a range of xe2x88x9280 to 100xc2x0 C., preferably xe2x88x9260 to 50xc2x0 C.
After completion of the reaction, the base can be removed from optically active imidazolidin-2-ones (4) by washing with water or acidic water. The desired product can be readily separated from the reaction mixture by a post-treatment such as extraction, phase separation, concentration and/or the like. The alkaloid and the aliphatic or aromatic tertiary amine compound may be recovered, for example, by adding a strong base to an aqueous phase obtained by washing the reaction mixture.